Method for controlling the blast furnace condition

ABSTRACT

Condition of a blast furnace is controlled on the basis of blast pressure index indicating the fluctuation of blast pressure in a predetermined period of time and/or descending rate index indicating the fluctuation of the descending rate of charged materials.

Tlnited States Patent [191 Yoshilii et al. I

METHOD FOR CONTROLLING THE BLAST FURNACE CONDITION Inventors: Michiyasu Yoshiki; Masanobu Ogata; Takashi Yokoi; Yoichi Murakami, all of Kitakyushu, Japan Assignee: Sumitomo Metal Industries, Ltd,

Osaka, Japan Filed: Mar. 2, 1973 Appl. No.: 337,690

Foreign Application Priority Data Mar. 15, 1972 Japan 47-27016 Oct. 14, 1972 Japan 47-103011 US. 01. 75/41 Int. Cl c211 5/00 Field of Search 75/41, 42

[4 1 Dec. 10, 11974 [56] References Cited UNITED STATES PATENTS 2,822,257 2/1958 Hanna et a1. 3,581,070 5/1971 Tsujihata et all 3,719,811 3/1973 Munson 75/41 X Primary Examiner-L. Dewayne Rutledge Assistant Examiner-M. J. Andrews Attorney, Agent, or FirmKurt Kelman [5 7] ABSTRACT Condition of a blast furnace is controlled on the basis of blast pressure index indicating the fluctuation of blast pressure in a predetermined period of time and /or descending rate index indicating the fluctuation of the descending rate of charged materials.

3 Claims, 13 Drawing Figures LAST STATE OF SOUND I N6 --F|RST STATE OF DISTANCE FROM STOCK LINE 1 SOUNDING PATENTEU 9.531

sum 1 m g DTSTANCE FROM STOCK 48O/288=L f LINE LAST STATE OF SOUNDING QWFIRST STATE OF STOCK LINE SOUND] N0 LAST STATE FIRST STATE OF OF soumome SOUNDING Fig. 4

TIME

/ O 500 L000 mm DISTANCE FROM STOCK LIT:

DISTANCE FROM STHER LINE PAIENIEQ mac 1 0 I974 SHEH 3%? Q v VA/ 500 LO OOmm DiSTANCE FROM STOCK LINE A! Mi;

A; xwaz; mFAE wzfizmumma NUMBER OF TIME OF SUP AND RARfiZL 'SLIPS PER DAY PATENTED 3,853,539

X .15 g 70 Z ws/ 3 L60 3 L55 5 L50 2 1,45 7 L40?" o 2 8 IO NUMBER OF TIME OF SLIP AND PARTlAL SLIPS PER DAY PATENTEL nan 1 mm SHEEI 7 BF Ill 0 0X 0 9 g a a m 00 w H m o 0\ M o m m o u o a w a u w 0 a u C 8 7 r0 5 4 3 8 8 8 8 8 8 3 $25 lo V05; KESIW PATENTEL 1 W 3, 853.539

sum S 0? I5 :16 If? (8 BLAST RRESSDRE INDEX This invention relates generally to a method for digitally judging and controlling the condition of a blast furnace, thereby stabilizing the furnace operation more effectively, and it relates more particularly to a new method for digitally controlling the condition of the blast furnace using the blast pressure index, the fluctuation of the blast pressure in a predetermined period of time and/or the descending rate index, the fluctuation of the descending rate of the charged materials.

It is a very important requirement in blast furnace operation to digitally judge the furnace condition every moment and to control it. In an attempt to make it possible to judge the furnace condition more precisely, efforts have been made to put together such factors as the blast pressure and charged material descending rate with long experiences of operators to control the furnace condition artificially. However, no successful method has been devised heretofore to provide a judgement digitally established and synthetically precise.

The most important among the various factors faithfully conveying the behavior of the blast furnace to the operators is the fluctuation of the blast pressure. It has been proposed to indicate the furnace condition expressions as Pb/V, (Pb-Pt)/V, or (Pb"'-Pt )/V where Pb: blast pressure, Pt: top pressure of the blast furnace, and V: volume of the blast furnace. However, these expressions are only for indicating the variation of the blast pressure with the blast volume rather than directly or digitally indicating the deviation of the indicated value, namely the fluctuation of the furnace condition which is the most important. It has also been proposed to indicate the furnace condition by bringing the values, such as number of times of hangings, slips, tuyer damages or volume of dust from the furnace top per unit time, as parameters into relation with the blast pressure or the blast pressure with the blast volume. However, none of these parameters is entirely successful ,in indicating the actual magnitude of the fluctuation faithfully.

SUMMARY OF THE INVENTION In the present invention, the fluctuation of the blast pressure is expressed by the amount of variation of the blast pressure in a predetermined period of time which is defined as the blast pressure index or the first furnace condition index. A significant correlation between this furnace condition index and the slips or partial slips is confirmed. A strong correlation is also confirmed between the strength and fine content of the sinter (-4 mm percent) and the drum index of the coke used in the blast furnace operation. Thus, we have found that the furnace condition index as defined above can be a standard for controlling the entire furnace condition digitally.

Further, in the present invention, the descending rate index or the second furnace condition index is adopted to express the fluctuation of the descending rate of the materials charged from the top of the furnace to thereby judge the furnace condition precisely and promote the highly stabilized operation of the blast furnace by using the descending rate index as another standard for controlling the entire furnace condition digitally.

Both furnace condition indices can, of course, be used at the same time to control the furnace condition precisely.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a portion of a strip chart recording the fluctuation of the blast pressure;

FIG. 2 is an enlarged partial view of a portion of the strip chart of FIG. 1;

FIG. 3 is a schematic diagram illustrative of an apparatus for measuring the descending rate of the charged materials;

FIG. 4 is a chart recording the descending rate of the charged materials measured by the apparatus shown in FIG. 3;

FIGS. 5A and 5B are charts recording the descending rate of the charged materials in which stable and unstable conditions of the furnace are shown respectively by 5A and 5B;

FIG. 6 is a graph showing the relation between the descending rate index and the number of slips and partial slips;

FIG. 7 is a graph showing the relation between the blast pressure index and the number of slips and partial slips;

FIG. 8 is a graph showing the correlation between the descending rate index and the blast pressure index;

FIG. 9 is a comparative representation of the furnace condition indices measured in a relatively long period of time; and

FIGS. 10 12 are graphs showing the correlations between each of the various properties of the sinter and the blast pressure index.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The blast pressure index or the first furnace condition index, as defined hereinbefore, is a value represented by the fluctuation length of the blast pressure in a predetermined period of time (Note: the blast pressure is a gauge pressure detected in the straight pipe between the hot stove and the circulating bustle pipe of the blast furnace. At a temperature of approximately 1, I50C, and the average gauge pressure is 2.1 Kg/cm The fluctuation length of the blast pressure is the actual length of the path of the pen recorded on the strip chart which is calculated by the method described below. Measurement of the fluctuation length is best wherein: 480/288 represents fluctuation length corresponding to the unit time, 5 minutes calculated from the scale of the chart;

248 represents width of the chart (full scale in millimeter) corresponding to the blast pressure fluctuation 4 Kg/cm (gauge pressure); and

480 represents fluctuation length corresponding to 24 hours of feeding of the strip chart (unit: millimeter).

The value X is obtained from the above equation l) and is approximately taken as the blast pressure fluctuation length L0. The blast pressure index or the first furnace condition index is obtained by dividing Lo by the length L (480/288) of the strip chart corresponding to the L0. Namely,

the first furnace condition index Lo/L 2 This index is calculated and typed out every hour, every shift (8 hours) and every day (24 hours).

The descending rate index or the second furnace condition index will now be described.

The descending rate of ore and coke charged from the top of the furnace indicates the fluctuations of the furnace condition. And digital judgment of such fluctuations contributes greatly to furnace operation by making it possible to judge the furnace condition objectively. Now, in order to digitallize this, the descending rate of every 1/2 charge, i.e. any one charge of either ore or coke into the furnace, (one charge being defined as one deposit of ore and coke.) is determined by the f w nssqsati n.Qua....

Descending Rate The first state) (The last state) of sounding of sounding fined as the value of the level at which a new charge of the materials must be made and the term the last state of sounding" is the value of the level when the charging of the new materials is finished. The level is measured with the furnace top side as the standard.

These values are indicated and recorded on a meter 5 by means of a sound rod 1, a take up drum 2, an electric motor 3 with a reduction gear, and a pulse generating motor 41 connected directly with the shaft of the take up drum, as shown in FIG. 3. The reference numeral 6 indicates a disengageable clutch. An example of such recording is shown in FIG. 4. The average value of the descending rate in a certain (standard) period of time is calculated, and the difference between each descending rate within the standard period of time is obtained, whereby the descending rate index or the second furnace condition index is defined as follows:

'Ihu second furnace condition index (NV-[(1) 'l (N2'K2) s' a) l' (NV-[(4) 1+ 2+ rtN4 wherein,

N,: Number of times when the absolute value of |(av- K K K and K are coefficients for weighting each measured descending ratedata by the magnitude of the deviation and are determined to be respectively: K, 3/3, K 4/3, K, 5/3 and K, 6/3. These weighting coefficients are predetermined so that the descending rate index is between 1.0 and 2.0 and that the descending rate index is identical substantially with the blast pressure index. Thus, the indices are calculated and indicated at every unit period of time and the average values of the indices are automatically calculated by means of, for example, an electronic computer, every 8 hours or 24 hours.

The descending of the charged materials is stable in FIG. 5A and unstable in FIG. 5B in which slipping and- /or partial slipping are occurring. The terms slipping and"partial slipping as used herein are defined to indicate respectively a sudden descending of the charged materials of not less than 1,000 mm in 5 seconds as marked X and I a less sudden descending within the range between 500 mm and 1,000 mm in 5 seconds as marked Y.

As a result of such definition, the average value of the descending rate index of 24 hours is found to be in substantial correspondence with the sum of the number of times of the slippings and partial slippings as shown in FIG. 6. In the axis of abscissa of FIG. 6, the number of times of slippings is weighted double that of partial slippings.

In FIG. 7, the first furnace condition index, namely the blast pressure index (average of 24 hours) is contrasted similarly with the number of times of slippings and partial slippings. FIG. 7 clearly shows that there is a relation as may be expressed by a curve of second order between them.

FIG. 8 is a graph showing a correlation between the descending rate index and the blast pressure index. Between these two indices there is found a high coefficient of correlation of 0.799. The suggestion for stabilized furnace operation according to the present invention shows that behavior of the blast furnace can be judged clearly and digitally by using the descending rate index of the charged materials and/or the blast pressure index.

For example, by measuring the behavior of either one or both of these indices over a long time as shown in FIG. 9, the degree of stability or instability of the furnace condition can be judged digitally.

In FIG. 9, each tuyer damage is indicated by a small circle. It is very interesting to notice that there is a strong correlation between the degree of the tuyer damage and the two indices.

Since one or both of these furnace condition indices are successively fed direct to the sinter and coke plants, when the behavior within the furnace runs into an unstable state, the following measures are taken. Firstly, the control level is raised, namely shutter index of sinter changes to not less than percent, fine content of sinter to not more than 6 percent, and further the quality of control standard is raised, namely drum index (Dl of coke increases to not less than 35/Secondly, the blast volume is reduced, for example, from 2,300 Nm /min to 2,200 Nm /min. When the furnace condition does not recover the desired stability even after the first and second measures are taken, the third measure is taken, namely the volume of ore per charge is reduced, for example, from 35,000 Kg to 30,000 Kg thereby improving the permeability within the furnace.

By these measures, a drastic aggravation or instability of the furnace condition can be prevented and a stabilized operation of the furnace for a long period is made possible. (Note: The figures referred to above as example are reference values of a blast furnace having the furnace volume of 1,350 m''.)

In order to give a more detailed description, correlations between the blast pressure index and each of the shutter index of sinter, the fine content of sinter and the drum index of coke are shown in FIGS. 12. In order to stabilize the furnace condition and maintain a smooth furnace operation, actions must be taken to hold the blast pressure index to not more than 1.50. The shutter index of FIG. 10 is defined as the rate of Kg sinter of oversize of 10 mm screening is dropped four times from the height of 2 m. The fine content of sinter of FIG. 11 is defined as the weight percent of undersize of not more than 4 mm screening. The drum index of coke of FIG. 12 is defined as the weight percent of oversize of 50 mm of coke of not less than 50 mm diameter, which is put into a drum having four vanes, rotated times at the rate of 15 rpm, and then screened by 50 mm mesh. As shown in FIGS. 10 12, these factors have significant correlations with the blast pressure index.

According to the present invention, the descending rate index and/or the blast pressure index are defined as the furnace condition indices serving as the operation standard of the blast furnace, fluctuation of the blast furnace condition is judged digitally over a long period of time, to thereby make it possible to take necessary measures quickly to stabilize the furnace condition. The present invention provides an appropriate guide to the computer-aided control of a blast furnace which is generally recognized to be difficult. Working of the present invention has a very great effect.

What is claimed is:

1. A method for measuring information during opera tion of a blast furnace, which comprises detecting blast pressure at a desired position in the blast furnace, recording the detected blast furnace pressure continuously on a strip chart, measuring fluctuation length of recorded blast pressure from the strip chart within a predetermined period of time thereby digitally expressing fluctuation of said blast pressure, determining a first furnace condition index by dividing said fluctuation length by the length of measured strip chart corresponding thereto, and applying said furnace condition index to judge the condition of the blast furnace and promote highly stabilized operation.

2. A method for measuring information during operation of a blast furnace, which comprises, measuring a first state of sounding, a last state of sounding and the respective times of the first and last states of sounding, said first state of sounding being the value of a level at which a new charge of material in said furnace must be made, said last state of sounding being the value of a level when the charging of new material is finished; calculating the descending rate of said charged material from the measured first and last states of sounding and the respective times thereof; averaging the value of said descending rate within a predetermined period of time, and obtaining the difference between the value of said descending rate and the average value thereof, thereby to obtain a second furnace condition index capable of judging the condition of the blast furnace.

3. The method of claim 2 wherein the second furnace condition index X is defined as follows:

Where N represents the number of times the absolute value of (average descending rate) (descending rate of every l/2 charge) is within 15 mm/min;

N represents the number of times said absolute value is within the range 15.1 mm/min 3O mm/min;

N represents the number of times said absolute value is within the range 30.1 mm/min 45 mm/min; and

N represents the number of time said absolute value is not less than 45.1 mm/min. 

1. A METHOD FOR MEASURING INFORMATION DURING OPERATION OF A BLAST FURNACE, WHICH COMPRISES DETECTING BLAST PRESSURE AT A DESSIRED POSITION IN THE BLAST FURNACE, RECORDING THE DETECTED BLASE FURNACE PRESSURE CONTINUOUSLY ON A STRIP CHART, MEASURING FLUCTUATION LENGTH OF RECORDED BLAST PRESSURE FROM THE STRIP CHART WITHIN A PREDETERMINED PERIOD OF TIME THEREBY DIGITALLY EXPRESSING FLUCTUATION OF SAID BLAST PRESSURE, DETERMING A FIRST FURNACE CONDITION INDEX BY DIVIDING SAID FLUCTUATION LENGTH BY THE LENGTH OF MEASURED STRIP CHART CORRESPONDING THERETO, AND APPLYING SAID FURNACE CONDITION INDEX TO JUDGE THE CONDITION OF THE BLAST FURNACE AND PROMOTE HIGHLY STABILIZED OPERATION.
 2. A method for measuring information during operation of a blast furnace, which comprises, measuring a first state of sounding, a last state of sounding and the respective times of the first and last states of sounding, said first state of sounding being the value of a level at which a new charge of material in said furnace must be made, said last state of sounding being the value of a level when the charging of new material is finished; calculating the descending rate of said charged material from the measured first and last states of sounding and the respective times thereof; averaging the value of said descending rate within a predetermined period of time, and obtaining the difference between the value of said descending rate and the average value thereof, thereby to obtain a second furnace condition index capable of judging the condition of the blast furnace.
 3. The method of claim 2 wherein the second furnace condition index X is defined as follows: X N1 + (4/3)N2 + (5/3)N3 + 2N4/N1 + N2 + N3 + N4 Where N1 represents the number of times the absolute value of (average descending rate) - (descending rate of every 1/2 charge) is within 15 mm/min; N2 represents the number of times said absolute value is within the range 15.1 mm/min - 30 mm/min; N3 represents the number of times said absolute value is within the range 30.1 mm/min - 45 mm/min; and N4 represents the number of time said absolute value is not less than 45.1 mm/min. 